Typical peak flow factors range from 4 to 6 for small
areas down to 1.5 to 2.5 for larger areas. An allowance
for unavoidable infiltration of surface and subsurface
water into the lines is sometimes added to the peak flow
to obtain the design flow. A typical infiltration allowance
is 500 gallons per inch of pipe diameter per mile of
sewer per day. From the types of sewage and the
estimated design flow, the engineer can then tentative] y
select the types, sizes, slopes, and distances below grade
of the piping to be used for the system.
Then preliminary drawings of the system are
prepared. The preliminary drawings should include both
plans and profiles of the proposed wastewater system
and all buildings, roads, waterways, utilities, geology,
and so forth, that may affect the design. As an EA, you
may be called upon to assist in the preparation of the
preliminary plans. When existing topographic maps of
sufficient detail are available, they may be used in
selecting the routing of the proposed system. However,
when existing maps are not available or to ensure
sufficient detail, you may be required to conduct
topographic and preliminary route surveying upon
which the routing will be based. The procedures for
these surveys are explained in chapters 8 through 10 of
this manual.
Upon acceptance of the preliminary designs, final
design may begin. During this phase, adjustments to the
preliminary design should be made as necessary, based
upon additional surveys, soil analysis, or other design
factors. The final designs should include a general map
of the area that shows the locations of all sewer lines and
structures. They also should include detailed plans and
profiles of the sewers showing ground elevations, pipe
sizes and slopes, and the locations of any appurtenances
and structures, such as manholes and lift stations.
Construction plans and details are also included for
those appurtenances and structures.
Q1.
Q2.
Q3.
Q4.
Q5.
Q6.
Q7.
Q8.
Q9.
Q1O.
QUESTIONS
Name the two systems that comprise an overall
power system.
What system of arranging primary feeders is the
least reliable but the most commonly used?
What is the purpose of a distribution trans-
former?
In relation to the primary mains, where on a
power distribution pole should the secondaris
be located?
Under what circumstances are concrete power
distribution poles authorized for use on a Navy
installation?
On a drawing of an overhead electrical dis-
tribution system what information should you
show for the overhead conductors?
Define water table.
What three primary factors must an engineer
consider when selecting a water source?
When, if ever, is it permissible to install a water
line and a sanitary sewer line in the same trench?
In a waste water system, what is the purpose of a
lift station?
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